1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device, and more particularly, to a method for forming a data line and a data line pattern in an LCD device while increasing device reliability.
2. Description of the Related Art
Thin film transistors (TFTs) are widely used as switching elements for pixels in a flat panel display device such as a liquid crystal display device or an organic light emitting display device. Liquid crystal display devices include a plurality of pixels, and each pixel includes a gate line to pass a gate signal (injection signal), a data line to pass a data signal, and a thin film transistor.
The thin film transistor includes a gate electrode coupled to the gate line, a source electrode coupled to the data line, and a drain electrode coupled to a pixel electrode of the pixel. These electrodes are formed over a semiconductor layer. The thin film transistor functions to transfer a data signal from the data line to the pixel electrode in response to a gate (injection) signal from the gate line.
In order to connect the pixel electrode with the drain electrode which is separated from each other with a passivation layer or passivation layer, a contact hole is made in the passivation layer, which is typically made of an inorganic matter, positioned over the thin film transistor.
During the manufacturing process of liquid crystal display device, a passivation layer is deposited over the data pad and drain electrode. However, the gate pad is covered not only by the passivation layer but also by the gate insulator.
Then, an etching process is applied to the photoresist layer. At this time, since the gate insulator as well as the passivation layer is over the gate pad, the passivation layer over the gate pad is first developed with the passivation layer over the data pad and the data electrode. Then, the etching process is applied to the gate pad to etch the gate insulator. During the process, the data pad and drain electrode are exposed to the etching process, so that the surface of the data pad and drain electrode is damaged.
Also, a contact hole over the data pad and drain electrode forms a reverse type taper structure, which is the structure as the higher up, the narrower in a cross-sectional area, so that the transparent pixel electrode may not connect well enough to the data pad and the drain electrode. Also, the etching process damages the surface of the data pad and drain electrode, which increases the contact resistance between the pixel electrode and the data pad or drain electrode. Therefore, the reliability and electrical characteristics of the liquid crystal display device are degraded.